This one shows all sorts of things including how Bing Audio works, YouTube video support (looks to work better within IE9), multi-tasking, messaging/history and some Xbox LIVE info (we like the part where the avatar punches and cracks the screen).

September/October can't come soon enough, that's for sure.

Update: Just got a nice tip from Antonio on this one. Check out the video around the 4:38 mark. In the XBox Live hub you see the option to "Pick a multi-player game and invite someone to play". Could this be the multi-player (phone vs. phone) feature? Any other new features hidden within the video?

Update 2: Oh look at that, we've always had that "notifications" page in our Xbox folder, but this does say "multiplayer" for the first time.